Earlier this week the Korean music world was hit with the sad news that pop-rock legend Shin Hae Chul had passed away from medical complications after suffering from a major heart attack.

An outpouring of condolences and support for Shin's family and friends immediately filled social media platforms as fans and colleagues in the music industry began sharing their favorite memories of the iconic singer.

On October 29, two days after his passing, it was revealed that Shin Hae Chul had one final gift for his fans. According to reports, the singer had teamed up with other legendary 90's musicians Seo Taiji, Kim Jong Seo, and Lee Seung Hwan for a secret music project dubbed '90's Icon.'

"Because the project was done in such secrecy, even the managers and companies did not know of it," revealed a representative from Shin's agency, KCA Entertainment. The company also said that Shin Hae Chul partnered with those specific musicians for the special project because "they were the ones who made the 90's in Korea more fruitful and musical."

Among his many musical pursuits, Shin was a member of rock band N.E.X.T, a group known as much for their varied performance styles as they were for their harsh cultural criticisms including 2004's "Dear America" that attacked U.S. political policies.

Seo Taiji is often considered to be the father of the modern K-Pop movement after his group, Seo Taiji and Boys, became South Korea's first successful boy band.  Before Seo Taiji and Boys rose to fame, Seo Taiji and Kim Jong Seo were both members of the Korean heavy metal band Sinawe. Kim Jong Seo later went on to launch a very successful solo career.

The "90's Icon" project's final member, Lee Seung Hwan, is one of Korea's most successful solo artists to date. He is said to have performed well over 1,000 live concerts since his debut in 1989 and his company, Dream Factory, estimates his record sales at more than 10 million.

The secret collaboration, said to have finished recording recently, was meant to be a new single for the aging stars who planned on releasing it immediately following mixing and mastering. Due to the sudden and tragic turn of events, however, it's release is still pending as the other artists determine the best time to reveal their friend's last song.